Background FOP is a rare but disabling condition characterised by congenital malformation of the great toes and progressive heterotopic endochondral ossification (HEO). FOP is the most catastrophic disorder of HEO in humans.

Flare-ups are episodic; immobility is cumulative. The discovery of the ACVR1 gene as the cause of FOP has allowed identification of possible therapeutic targets. Palovarotene, a retinoic acid receptor gamma agonist, is currently in Phase 2 clinical trials to reduce HEO during acute flares.

Aim To describe the clinical presentation and current management of FOP.

Methods A 7 year old boy with a history of hallux valgus, recurrent painful episodes of soft tissue swelling and new abnormal bone formation, was assessed clinically and radiologically.

Results Review of the clinical history and radiographs taken in infancy revealed the diagnosis of FOP. This had not been previously recognised, although he had been seen in a specialist Hallux Valgus clinic as a baby.

Conclusions As specific treatments are now becoming available for this life-limiting condition, it is essential that all neonatologists, paediatricians, paediatric oncologists and orthopaedic surgeons consider a diagnosis of FOP if a baby or child presents with bilateral hallux valgus and/or episodes of swelling with evidence of ossification. These children should now be referred to a paediatric metabolic bone clinic to consider genetic testing and for specialist management.